The glycoprotein hormone erythropoietin is a prime regulator of red cell production in higher organisms. The hormone is produced in the kidney in response to hypoxia, for example, as a response to anemia. It would be of great value to have an immunoassay to monitor erythropoietin levels in people suffering from anemia, pulmonary insufficiency, renal tumors, etc. At present, although both monoclonal antibodies and polyclonal antibodies have been raised to erythropoietin, no efficient immunoassay based upon the (preferred) monoclonal antibody technology has been developed. The specific aim of this proposal is to develop a panel of monoclonal antibodies to erythropoietin, to be used in the design of an immunoassay appropriate to the clinical laboratory.